Output password in email

I'm still grappelling with my Tag problem but in the meantime could you tell me how I output a members password to the new_member_notification.html email. I've tried $memberPassword and $password but neither give me the right result?

<p style="font-size:16px; font-family:Helvetica, sans-serif; color:#58595B; font-weight:lighter; line-height:1.5em; margin:0 0 20px 0; padding:0 0 0 0;"><b>$first_name $last_name</b> <br />$memberEmail<br />Password: $memberPassword</p>